This invention relates to the field of connectors, and particularly to means for joining two tubular conduits in end-to-end relation to give a tight and rigid joint. The invention may be used where the members are of the same diameter and are simply butted together, where one member is slotted to telescopically receive the other, or where one member is a rigid tube and the other is a flexible hose into which the first is inserted, the latter two cases of course involving tubular members of different although approximately the same diameter, the difference being the wall thickness of the outer tubular member or hose.
Although the invention is generally applicable with tubing and hoses of widely varying compositions, we have chosen to illustrate it as used with the rigid and flexible metal tubing and hoses associated with the exhaust systems of commercial trucking equipment, having diameters ranging mostly between two inches and six inches. In this field one tubular member is conventionally inserted into another and secured there by tightening a U-bolt against a semi-circular shoe, in what is known as a quillotine clamp or saddle clamp. This arrangement has the drawback that it deforms the cross sections of the tubes from circular to elliptical, so that stresses are not uniform and so that gases and sound leaks directed paraxially, that is, parallel to the axes of the members, frequently result. A further defect of the arrangement is that the narrow U-bolt frequently dimples the outer tubular member into the inner one, in such a fashion that when the U-bolt is removed it is impossible to disassemble the complete system without cutting the metal. Again, the U-bolt arrangement is very severe in its action on flexible metal hose, while at the same time being relatively inefficient in preventing leaks along the helical grooves in such hoses.
Efforts have been made to overcome the defects of U-bolt type clamps by use of closed cylinders generally of internal diameter to match the outside diameter of the tube being clamped, and with means for contracting the cylinder to give circumferential force acting substantially all the way around its periphery. A packing strip of some sort is desirable to seal the paraxial gap associated with the closure means. Such clamps must be positioned at the time the piping system is being assembled, although they need not be tightened until later, and they cannot be replaced without disassembling the system. Other structures are known, such as that disclosed in the Fortune U.S. Pat. No. 3,411,748, wherein a split cylinder of appropriate diameter is provided with ears which are pulled together to produce the necessary circumferential clamping force.
None of the prior art devices known to applicants have been suitable for use in joining tubular members of different sizes, as is necessary when one tube is inserted within another. Because of this it has been necessary to specially construct stepped clamp diameters to fit the two tubes being joined, one around the outside of a larger tube at its end, and one around the outside of the smaller tube where it emerges from the other. Sizes and modifications tend to proliferate in such structures to the point where mass production is no longer economically feasible.